This invention relates to deployable countermeasures, and more particularly, to a system for the deployment and retrieval of a towed decoy.
As will be appreciated, aerial towed objects are used for a variety of purposes, including decoys, testing, and scientific investigations. In one embodiment, the decoys are used to draw various types of guided weapons away from an aircraft that the weapons are intended to destroy. These towed targets and decoys typically contain various types of electronic circuits to create an apparent target to a weapon in order to attract the weapon to the decoy rather than the aircraft. One such active electronic device is a traveling wave tube amplifier equipped transponder to which high voltages must be applied to power its traveling wave tube. Additionally, other controls for the traveling wave tube or other electronics in the towed object are transmitted in one embodiment along a fiber-optic transmission line, which is both fragile and frangible.
In the past, it has been the practice to pre-deploy the decoys such that when an aircraft arrives at a hostile area, the decoys will already be in place and capable of performing their intended countermeasure function. Typically, these decoys are deployed in a relatively slow manner, often taking several minutes for the decoy to arrive at a predetermined distance behind the aircraft.
When missions can last, for instance, for as much as six hours, there are aircraft range considerations involved in predeployment, as well as potential restrictions placed on aircraft with a decoy in tow.
Thus, in combat situations, when an aircraft is entering into hostile territory, one or more decoys are towed behind the aircraft until such time as the aircraft leaves the hostile territory. Thereafter, the decoy is cut loose from the aircraft and sacrificed.
There are obviously two problems associated with such a system. First, flying around with a decoy could limit the range of the aircraft as well as possibly requiring limits on the, types of tactical maneuvers that the aircraft can perform. Secondly, sacrificing the towed decoy at the end of the mission is both expensive and results in inordinate delays in reprocurement.
In general, it would be desirable to only deploy the decoy round when a threat has been sensed and to be able to retrieve the decoy round for redeployment during the same combat mission as additional threats are detected.
By way of further background, the typical manner of deployment is such that when a decoy has fulfilled its function, it is simply cut loose. For this purpose, the fiber optic wires and the high tension line are severed, with the severing taking place after the high voltage has been removed and after all usable signals along the fiber optic cable have been terminated.
The practice of cutting loose decoys after use and using them as an expendable commodity causes the above-noted problems. As a result it becomes important to be able to recover the towed decoy itself, mainly because of the cost of the towed vehicle, as well as the fact that replacing towed vehicles often is difficult due to the long lead times for the manufacture and provision of such decoys.
For instance, typically a towed counter-measure decoy may cost as much as $50,000 per decoy round. As many as eight decoys per sortie or mission can be deployed and as such, assuming 400 sorties per month, then the total expense of deploying expendable decoys is quite large, making the cost for the protection of the aircraft that employs these decoys excessive. Moreover, in a wartime setting, the decoy cannot be manufactured quickly enough. So bad is the situation that it may be necessary to scrounge used decoys from the battlefield where they fall.
It will be appreciated that prior to the subject invention, the only type of retrievable devices from aircraft were the sonobuoys that were dropped from helicopters on a line and then winched back up into the helicopter itself. Another type of towed device was an air speed head that was used to measure a variety of parameters behind an airplane. These types of devices were winched back into a pod on the aircraft in a conventional manner. In the above examples of winched-in sonobuoys or towed instruments, the instruments were never used in any kind of airborne counter-measure environment. Thus they were not carried in such a manner that they could be rapidly deployed in a battlefield scenario. Certain types of countermeasures were tested using 5-6 foot long test pods. However, the apparatus proved too large and cumbersome for tactical employment.
Note that the above airborne-winch systems are incompatible with deployment of towed decoys and current volume constraints on tactical aircraft, both due to size and due to problems with slowly winching out a drogue or towed vehicle of any kind. Further, sonobuoys and pod-mounted countermeasures typically were carried in an equipment pod the size of the MK-84 aerial bomb or the ALQ164-type electronics counter-measures pod. What will be appreciated is that these pods are exceptionally large and preclude, for instance, the carrying of armaments in the position where a pod is located. Thus, the payload of any attack aircraft would be severely limited if one were to use such unwieldy winching systems along with housings that are many times the size of a normal decoy round.
There is therefore a need for a compact launching and retrieval system for decoy rounds with an improved and miniaturized winching mechanism that would permit both rapid deployment of the decoy while at the same time being able to reel in the decoy and permitting it to dock so that it can be redeployed.
By way of further background, the types of decoys involved have included devices which counter-measure infrared guided and radar guided missiles that pose the primary threats to military aircraft engaged in a combat environment. Note that these missiles use their radar guidance systems to get within striking distance of the aircraft, thereby substantially increasing the probability that the IR system on the missile will be able to lock onto the target.
Current military aircraft are particularly vulnerable to attack from IR-guided surface-to-air and air-to-air missiles. Statistical data of aircraft losses in hostile actions since 1980 show that the majority of these losses have been the result of IR-guided missile attacks. As a result, the ability to deploy, recover and redeploy decoys that can counter-measure the IR guidance systems on these missiles is of great value to protect aircraft during combat situations. As mentioned above, the IR-guided system initially utilizes radar guidance and then switches over to IR guidance as they come into closer proximity to the target. If one can counter-measure the radar system, then the IR portion can never lock onto the particular infrared target. To do this, the missile is deflected away by generating a signal that causes the radar guidance system in the missile to think that the target is actually elsewhere than it actually is.
In the past the ALE-50 Towed Decoy system currently in the inventory of the US Armed Forces includes a decoy round in a canister and a reel payout mechanism. When the decoy has served its purpose, it is cut loose and the ALE-50 decoy is lost.
Moreover, the same scenario is true for the more modern ALE-55, or in fact, any type of expendable towed vehicle.
As will be appreciated, there are a number of US patents that in general cover towed vehicle deployment, such as U.S. Pat. Nos. 5,836,535; 5,603,470; 5,605,306; 5,570,854; 5,501,411; 5,333,814; 5,094,405; 5,102,063; 5,136,295; 4,808,999; 4,978,086; 5,029,773, 5,020,742; 3,987,746 and 5,014,997, all incorporated by reference herein.
In summary, prior art decoys were predeployed and towed for the entire duration of the mission after which they were cut free after exiting hostile territory.
In order to change the entire tactical strategy in which decoys are deployed, in the subject system, decoys are deployed at the time when a threat is sensed, with the rapid deployment method described herein permitting the decoy to be deployed in seconds, rather than in minutes. This is sufficient time for the decoy to be effective in thwarting an attack. After the threat has ceased, the decoy is retrieved by reeling it in so that it can be deployed again.
The system contemplates single and multiple cable use, with the deployment system to be described permitting the use of fragile fiber-optic cables and eliminates the necessity of using fiber-optic rotary couplers. In a multi-cable embodiment, the fiber-optic cable is wound around a tow cable when the decoy is deployed, with deployment and retrieval, done in such a manner that damage to the fiber-optic cable is kept to a minimum.
For the more complicated multi-cable embodiment, deployment or payout of the dual cable system is accomplished through providing both a tow cable and a fiber-optic cable wound around respectively a rotating spindle with a rotationally fixed bail and a rotationally-fixed bobbin with a rotating pickoff. The takeoff apparatus which removes the cables from the respective spindle and bobbin is mechanically linked or ganged together such that the payout of the towing cable matches the payout of the fiber-optic cable to prevent cable damage.
When a warning receiver indicates an imminent threat, the output of the warning receiver is applied to a control unit which is in turn coupled to a transmission to drive a solenoid braking bobbin is mechanically linked or ganged together such that the payout of the towing cable matches the payout of the fiber-optic cable to prevent cable damage.
When a warning receiver indicates an imminent threat, the output of the warning receiver is applied to a control unit which is in turn coupled to a transmission to drive a solenoid braking system for controlling the speed of rotation of the spindle and the pick which rotates with the spindle so as to pick off or unwind the fiber-optic cable carried on the non-rotating bobbin as the bobbin translates back and forth. The unwound towline goes through the center of the spindle where the unwound fiber-optic cable meets it and is wound around the tow cable during deployment in a helical fashion.
The speed at which the tow cable is deployed is controlled by the brake on the spindle, whereas a double helix pick translation mechanism driven by the rotating spindle causes the unwinding of the fiber-optic cable from the bobbin in lock step with the deployment of the towing cable.
The speed of deployment, in terms of how much cable per second exits the canister housing the system is controlled by the braking system for the rotating spindle which houses the tensile member.
Since the pick for the bobbin housing the fiber-optic cable controls the speed of deployment of the fiber-optic cable and moves with the rotation of the spindle, there is a mechanical linkage that results in synchronization of the speeds of deployment of the fiber-optic cable and the speed of deployment of the towed cable to a good approximation, thus controlling stress imparted on the fiber.
In the case of the bail which is utilized to remove the towing cable from the spindle, the bail translates back and forth so that the cable which is helically wound on the spindle is removed in a
In short, for the dual cable embodiment, there are two level-winding and unwinding devices associated respectively with the spindle and the bobbin which control the synchronization between the deployment and retrieval of the tow cable and the deployment and retrieval of the fiber-optic cable.
Because the fiber-optic cable is carried on a non-rotating bobbin, there is no necessity for a fiber-optic rotary joint, or other type of dynamic optical interface, to be able to connect control signal generating apparatus to the fiber-optic cable. The new re-usable countermeasure system thus provides significant benefits in terms of cost and logistics, while minimizing aircraft installation and performance penalty.
In summary, a fast deployment and retrieval system permits the rapid deployment of a decoy in seconds in response to an incoming threat, thus eliminating, the necessity of pre-deployment, with retrieval permitting reeling in and deployment of the decoy round a number of times during a mission in response to threats. Upon detection of an incoming threat by a warning receiver, a controller coupled to a transmission releases a brake that is utilized to control the speed of deployment, whereas upon retrieval, the transmission drives a motor for retrieval of the decoy. The system is thus reusable, fast reacting and also minimizes range considerations because the decoy is only deployed when needed. In one embodiment, the system accommodates both a towing cable and a fiber-optic signal cable in which apparatus for unwinding of the cables is mechanically ganged together so that the cables pay out at the same rate. This type of payout lowers the stress on the fragile fiber-optic cable making possible multiple deployments and retrievals in response to separate threats during a mission.
For the multi-cable embodiment, deployments in seconds versus minutes is accomplished through the utilization of a spindle that carries the tow line and a translating bobbin that carries the fiber-optic cable, with the fiber-optic cable being wound around the tow cable as the dual cables fiber-optic cable, with the fiber-optic cable being wound around the tow cable as the dual cables are deployed. In one embodiment, a bobbin-pick combination stores, deploys and retrieves the fiber-optic cable, whereas a spindle-bail combination stores, deploys and retrieves the tow cable. The relative speeds between the bobbin-pick combination and the spindle-bail combination are adjusted through a mechanical linkage that gangs together the two mechanisms so that the two cables, are deployed at matched payout speeds.